Exhaust gas generated from combusting an air/fuel mixture within a cylinder of an internal combustion engine is a heterogeneous mixture that contains gaseous emissions. The gaseous emission include, but are not limited to, carbon monoxide (“CO”), unburned hydrocarbons and oxides of nitrogen (“NOx”) as well as particulate matter comprising condensed phase materials (liquids and solids). Combustion of the air/fuel mixture in the cylinder can burn off an amount particulate matter before the exhaust gas exits the vehicle. In the case of compression-ignition engines such as, for example, diesel engines, the air/fuel mixture autoignites based on the pressure and temperature within the combustion chamber of the cylinder. The temperature in the cylinder, however, can affect the amount of particulate matter that is burned off. For example, excessive retardation of the spark relative to the piston position may result in an inefficient burn-off of the particulate matter thereby increasing the emissions output of the engine.
Conventional methods of controlling air/fuel combustion to drive the engine are based solely on the pressure within a respective cylinder. More specifically, conventional combustion control systems sample the cylinder pressure with respect to specific positions of the piston indicating the properties of the thermodynamic cycle. However, the numerous pressure and piston position measurements are time consuming. Further, the pressure measurements may not accurately distinguish the pressures within two or more cylinders among a plurality of operating cylinders.